Compare the scans side-to-side. The left photo below is the original
scan using manual settings. The photo on the right is done with VueScan,
setting the white and black points to automatic.

Look at the faces, and the wallpaper around the man's head. As you can
see, the image on the right preserves much of the detail lost in the image on
the left. We could have obtained the scan on the right by manipulating the
brightness and contrast settings manually (but why go through the trial and
error, IMHO). The following pair of images are based upon the two images
above, using the brightness curve to get the best image that I could from
each. I also sharpened both images (using the Unsharp mask command, radius
2, threshold 6 - see Case 1). For the image on the right, I increased the
contrast in the darker portions of the photo, and lessened the contrast (and
darkened a bit) the highlights around the faces. I tried similar changes
on the image on the left, to the extent I was able to. Again, the image
based upon the original scan is on the left, and the one done using VueScan is
on the right.

If you start with a better scan, you get a better final image.

Since we have covered much of general image editing in the first 2 cases, I
thought that I would do a few brief cases (such as this one) focusing on points
of particular interest or which present particular challenges. So, expect
to see a few more short cases in the near future. As always, please let me
know if you have any comments.